The Drillers Method
In the Driller's Method, the kick is circulated out of the hole using the existing mud weight. The mud weight is then raised to the required level and circulated around the well.
Two complete circulations are thus required, as a minimum, for this method. Since it deals separately with the removal of the kick and the addition of kill weight mud, it is generally considered to be the simplest of well control methods, and it requires least arithmetic. However, this results, in the well being circulated under pressure for a relatively long time, possibly the longest of the three methods, with an increased possibility of choke problems. Also, the annular pressures produced during the first circulation are higher than produced with any other method.
CAUTION: because very high annular pressure may arise when killing a gas kick with this method, care should be taken. Annular pressure will be at a maximum immediately before gas arrives at surface, and casing burst pressure limitations may be critical.
This method is most used on small land rigs where the Driller may have little help and limited equipment. It is also used on highly deviated and horizontal wells, where the influx is likely to be a swabbed kick.
In addition the simplicity of the Driller's Method makes it useful when only limited information is available about the well conditions.
To summarise:
FIRST CIRCULATION: Pump the kick out of the well, using existing mud weight. SECOND CIRCULATION: Pump kill weight mud around the well. Advantages of Driller's Method:
- Minimum Arithmetic
- Minimum Waiting Around Time - can start kill at once
- Minimum Information Required
Disadvantages of Driller's Method:
- Highest Annular Pressure Produced
- Maximum Well Under Pressure Time
- Longest 'On-choke' Time r
SECTION 5 : METHODS OF WELL CONTROL
Procedure for Driller's Method (See Figure 5.2)
- The well is closed in and the information recorded. FIRST CIRCULATION
- If a slow circulating rate pressure, Pscr, has been taken, then calculate the pressure required on the drill pipe for the first circulation of the well.
This is: Initial Circulation = Slow Circulation Rate + Shut-in Drill pipe Pressure Pressure Pressure or: ICP = PSCR + SIDPP
- Open the choke about one quarter, start the pump and break circulation; then bring the pump up to the KILL RATE.
- While the Driller is bringing the pump up to the KILL RATE, the choke operator should operate the choke so as to keep the casing pressure at or near the closed in casing pressure reading.
- Once the pump is up to the KILL RATE, the choke operator should transfer his attention to the drill pipe pressure gauge and adjust the choke to maintain the INITIAL CIRCULATING PRESSURE on the drill pipe pressure gauge.
- The INITIAL CIRCULATING PRESSURE is held constant on the drill pipe pressure gauge by adjusting the choke throughout the whole of the first circulation, until all of the kick fluid has been circulated out of the well. The pump rate must also be held constant at the KILL RATE throughout this period.
- Once the kick is out of the hole, shut the well in and mix up the kill mud weight required.
Kill Weight Mud (ppg) = Original Mud Weight +
NOTE 1: This is a kill weight mud to balance formation pressure. It is the lowest possible mud weight which will 'kill' the well. Once the well is dead, it will be necessary to increase the mud weight further to provide a trip margin.
NOTE 2: Some operators prefer to continue circulating the well while kill weight mud is being mixed. There is no theoretical reason why this should not be done, though it does result in further wear and tear on equipment under pressure - in particular the choke.
Gas Kick
DRILLER'S METHOD
KICK SHUT IN
Gas Kick
DRILLER'S METHOD
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